A method for transmitting a secondary advanced-preamble (SA-preamble) from a base station in a wireless communication system is disclosed, wherein the SA-preamble supporting an irregular system bandwidth. The method comprises allocating a plurality of sequence subblocks corresponding to a regular system bandwidth; configuring the SA-preamble by dropping one or more sequence subblock pairs among the plurality of sequence subblocks symmetrically in base of a DC component; and transmitting the SA-preamble to a mobile station, wherein a bandwidth of the SA-preamble is same as or narrower than the irregular system bandwidth.